Electrical distribustion system



Feb. 26, 1929 1 703 1 1 H. R. woonRow v ELECTRICAL DISTRIBUTION SYSTEM Original Filed Dec: 1, 1925 Inventor: Harry RWOodPoW,

His Atto meg.

contra-air, .5.

L It. WG GDEU'W, @lfi BROOKLYN, NE'W YORK, ASSIGNOR TU GENERAL ELECTRIC CORPURATION OF NEW YORK.

ELEG'EatIfiZ-llh DISTRIBUTION SYSTEM.

Application filed. inecernber l, 1925, Serial No. 72,592. Renewed July 17, 1928.

tem proi ided with a plurality of high-volt age feeders, a failure of one of the feeders does not necessarily cause a failure of load supply to the network, since the sound feeders may be capable of maintaining continuity service. However, if a feeder is disconnected its source of supply or a short circuit occurs in the feeder. a reversal of energy flow will occur in that feeder as a result of the network supplying the magnetizing cur rent for the transformer, or as a result of the network feeding power into a. fault or short circuit on the feeder. It then becomes necessary to disconnect the distribution transformer to prevent feed back of energy from the network, and it is also desirable to reconnect the distribution transformer to the network when normal conditions have been restored.

Di-liiculties have arisen in providing a niechanisn'i, which is simple and reliable in operation, to disconnect the distribution transformer from the network on reverse energy low because of the great range of current valuesencountered, namely, a comparatively small value of magnetizing current and the high value of current due to a fault or short circuit fed from the network.

it is, therefore, an object of my invention to provide an improved means, which is simple. hip'hly responsive, and reliable in operation, for. disconnecting distribution transformers from a network on a reversal of energy flow and reconnecting the transformers to the network when normal conditions have been restored.

For the purpose of explaining the present invention, it has been illustrated in the accompanying drawing as applied to an alternating-current distribution system with an interconnected secondary system, but it will be understood that it may be applied to other systems of electric distribution and in new eral to two interconnected alternating-current circuits subject to a reversal. of energyv flow between the circuits.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended. claims, the invention itself, however, both as to organization and method of operation, together with further objects and advantages thereof will be best understood by reference to the following description taken in connection with the accompanying drawing in which the single figure is a schematic illustration of alternating-current distribution system which my invent-ionhas been embodied.

Referring to the drawing, 1 indicates'tho primary highwoltage mains of a distribution system connected-to high-Voltage feeders 2, supplying distribution transformers which are interconnected on their low-voltage sides by the distributing network 4. Circuit breakers 5, of any suitable type, are interposed in the main feeders while network circuit breakers 6 are provided'in the low-voltage mains 7 connected to the secondary windin of the distribution transformers. In order to simplify the disclosure, only one feeder is shown equipped with the apparatus for effecting the automatic disconnection and reconnection of the transformer secondary, but it will of course be understood that each feeder, or any desirable number of feeders. may be similarly equipped. An impedance 8. which is preferably an inductive appara tus, is inserted in series with the circuit breaker 6. Preferably ll use a reactance arranged to saturate at a low value of load current so as to limit the current through the current coil and prevent excessive heating thereof under any value of load current attained during the operation of the system.- A network relay 9 of the power-directional type is connected tocontrol the operation of the network circuit breaker 6. Relay 9 is shown as comprising a voltage coil 10, a current coil 11, a contact 12, and'contact points 13' and 14;.

For simplicity of illustration, l have shown a secondary network which has one side th ereof permanently connected to ground. One terminal of voltage coil 10 is grounded at 15 while the other terminal thereof is connected to the network. The current coil ll. is connected to the transformer-side of the device 8 and to the other side of the switch 6 through an adjustable impedance, shown as a resist ance 16, which is used to limit the currentthrough the current coil 11 when circuit breaker 6 is open. The coil 11 is referred to herein as a currentcoil in order to differentiate clearly from the voltage coil 10, but

y from the description.hereinafter it will be apparent that the coil' though responsive to current might be considered a voltage coil when circuit breaker 6 is open, since it is subjected to the difference in voltage resulting from the difference in magnitude and phase of the voltage between the transformer secondary and the network. Furthermore, the dual function performed by the single coil 11 eliminates an operating coil and makes the arrangement more sensitive to trip out the tact points 22 and 23, and a contact 24 having contact points 25. The adjustable resistance 16 is connected across the contact points 25. The closing coil 17 is connected toth'ecir cuit-breaker side of the device 8 in ordentoi avoid a periodically opening and closing of the circuit breaker on an attempted reconnection. The closing coil 17, takes a compara.

tively large operating current and a part of this current will be supplied from the network as soon as the tips of the circuit breaker touch the breaker contacts. If the closing coil were connected to the feeder between the device 8 and'the transformer secondaigy tghe current supplied by the network would flow through the device 8 in the reverse direction and produce an opening torque in the power directional relay.

. With the above description of the ap iaratus in mind, a better understanding 0 the various circuit conditions at different points of the cycle of operations may now be obtained. Assume that the network is energized by means of one feeder and that the other feeder has been'disconnected by moving circuit breakers-5 and 6 in that feeder to the open position. Vo1tage coil 10 will be energized from the network and current coil 11 Wlll be energized by a reverse current flow in a circuit from the network, through resist;- ance 16, current coil 11, conductor 7, the secondary of transformer 3, to the" ground-15.'

Contact 12- of relay 9 will now be subjected to an actuating torque and is arranged to close contact points 14. If

5. is now closed, the primary of transformer 3and thereby its secondary -fiill+be-enercircuitgiboig gized fromthe supply mains 1. With.circuit breaker 6 in the open position, current coil 11 is in a series circuit between the t br es 1 3 in phase with the network voltage so as to 1 permit energy'flow from the transformer secondary to the network, the current coil 11' cooperating with the voltage coil 10 will move contact 12 to bridge its contact points 13. With circuit breaker 6 in the open posi tion, contact 21 bridges its contact points 23 anda circuit willv be completed for the circuit breaker closing coil 17 from transformer 3, the main 7 the device 8, contact 1'2, con tact 21, coil 17, to the other side of the system, shown as a ground 15. Coil 17 is now instrumental in moving circuit breaker 6 to a. circuit closing position and the latch 20 takes its illustrated position and holds the breaker closed.

As soon as circuit breaker 6 closes, power flow is from the transformer 3 into the net- 'work and current flows through the device 8 inserted in series with the line to the network. 7 The'c'iirrent coil 11 is now energized in accord-- jancewith[tlmdirection of current in the device 8 an maintains contact 12 in the position takeneinitiallye, In this position of circiiitbfeakeTtifiTpdrtion of the impedance 16 in series with the current coil is shortcircuit-ed by contact 24 which bridges the contact points 25 connected to one terminal of the impedance 16 and an adjustable slider 26. A-portion of the impedance 16 remains in sci tllj1ll-hgfonnd dgs irable in order to maintain the proper phasa rdlation of the current in the current coil 11. In some cases the impedance 16 may be somewhat inductive with advantage.

Now if feeder 2 is deenergized by opening circuit breaker 5, transformer 3 will be magnetized from the net work and a reverse current will flow through'the currentwinding 11 which cooperates with the voltage coil 10 to move the contact 12 to bridge the contact points 14'. This movement of the contact 12 completes a circuit for the opening coil 18 from the line 7, Contact 12, contact 21, coil 18, to the other side of the system, shown as a ground 15. As soon as coil 18 is energized the plunger 19 is move'ctto a position to disengage the latch 20 and circuit breaker 6 'moyes to its open positionfhereby breaking thecircuit through theopening coil 18. This movement of thebreaker causes its ntact ithe circuit gcoil 17"and,opens the short- W i 'esist-ance 16. The current-coil with a high resistance in series therewith is now the only connecting link between the deenergized feeder and the offl e "cl'iisin ns work. The same cycle of operations will to to a fault or short circuit in feeder 2',

l Vhen circuit breaker 5 is closed and the conditions of potential, both as to magnitude and phase, are such as to permit energy flow from the primary mains to the network, co rent coil 11 will be instrumental in moving contact 12 to bridge its contact points l3. A w circuit is again completed for the closing coil 17 and circuit breaker 6 will is removed to its circuit closing position in the same manner as described before the reversal of energy flow. While in the foregoing there has been.

shown and described the preferred embodinie of this invention, it is to be understood that changes in the details of construction, combination, and ariangement of parts may or; be resorted to without departing; from the spirit and scope of the invention as claimed. hat claim as new and desire to. secure. by Letters Patent of the United States, is,

transformer circuit controlling sys- .25 tom to alternatingcurrent networks wherein a is provided for connecting disconnecting; secondary oi the trans former and the netwo k in accordance with the direction ciurent flow in the trans i'ornier secondary, comprising in combination a directional provided with a voltresponsive winding and only one current responsive winding, an inductive apparatus connected in series with the switch between network and the transformer second ctly in circuit connected around said ictive apparatus and switch, there being; no conne ion to'said current winding be- .1 nduct ve apparatus and switch hen the switch is open said cur-- tinding energized in accordance with i the current Flowing in said whereby when the switch. is closed current winding is energized in with the direction of current i. ve l v circuit controliing 'sy. zeriuiting-current networks where enetwork in accordance with current flow the ner second ,7, ccmprisin combinaprovic I h rsive windingand current coil minals connected respectiveiy to the transformer secondary is directly connected in between said network and said trans- $021138? impedance in series r the current when S3116. 1 7

through current c its place tor a reversal of energy flow due lid current responsive winding being is provided connecting andthe secono'ary'oi the trans greed i relay to effect closing of saidswitch when current flows from said transformer second ary to said network, and an inductive appuratus' connected in series with the switch bctween said network and transformer secondary, said inductive apparatus and switch being between the points of connection of said current coil to the network and transformer secondary whereby said current coil is encr- -necting said electriccircuits, an inductive apparatus in series relation with said switch, and a directional relay comprlsmg a voltage responsive inding and only one current coil,

said current coil being connected in shunt with the portion of the circuit which includes said inductive'apparatus and switch in series 1 99 I and adapted to be energized in accordance with the direction of current flow in said inductive apparatus when said switch is'closed and being directly in a circuit between said electric circuits so as to be energized in accordance with the difference in magnitude and phase of the voltage between said electric circuits when said switch is open, said current coil cooperating with said voltage responsive winding to operate the relay for 100 eiiectinr; closing oi said switch when current flow is in one direction between said electric circuits and for effecting opening of said Switch when current flow is in the reverse direction between said electric circuits. A transformer circuit controlling system for alternating-current networks wherc a switc is provided. for connecting and disconi the secondary of the transformer an the network in accordance with Y on of current flow in the transformer secondary, comprising in combination a directional relay provided with a voltage responsive windiin;- and only one current responsive winding, an impedance connected in series it he switch between said network and the si ormer secondary, said current responsive wir being directly in a cir cuit connected around said impedance a switch, there being no (JOYHlGCtlOIl-lii) said current responsive winding between said impeo 21 whereby when the switch is open said current responsive winding; is enerance with the direction of the in said circuit, and whereby 1 e si itchis closed said currentl responsive winding is energi'zedin accordance with the cnrection of current in said im former circuit controlling sys- W1 former secondary, comprising in Combination adircctional relay provided with a Voltage responsive winding and only one currentresponsive winding. a reactance connected in series with the switch between said network and the transformer secondary, said current responsive winding being directly in a circuit connected around said reactance and switch,

, there being no connection to said current responsivewinding betwecnsaid reactance and switch whereby when the switch is o peii'said current responsive winding is energized in accordance with the direction of the current flowing in said circuit, and whereby when the switch is closed said current responsive winding is energized in accordance with the direction of the current in said reactauca 6. In combination, two alternating-current electric circuits, a switch for interconnecting said electric circuits, an inductive apparatus in series relation with said switch, a direc-..

tional relay comprising a voltage responsive winding and only one current responsive winding, an impedance connected in series relation with'sai'd current responsive winding, and'means for effecting avdecrease in the amount'of said impedance in the circuit of said current responsive winding when said switch is closed and for effecting an increase in the amount of said impedance when said switch is open, said current responsive winding being adapted to be energized in accordance with the direction of current flow in said inductive apparatus when said switch is closed and being directly in a circuit between said electric circuits so as to be energized in accordance with the difference in magnitude and phase of the voltage between said electric circuits when said switch is open.

7. A transformer circuit controlling sys tem for alternating-current networks wherein a switch is provided for connecting and disconnecting the secondary of the transformer and the network in accordance with the direction of current flow in the transformer secondary, comprising in combination a directional relay provided with a voltage responsive winding and a current responsive winding with its terminals connected respectively to the network and the transformer secondary whereby said coilis directly connected in a circuit between said network and transformer secondary, an impedance connected in series with said current coil for limiting the current to the current coil when said switch is open, auxiliary switching'means associated with said switch and arranged for short circuiting said impedance when said switch closed and inserting said impedance when said switch is open, said current coil cooperating with said yoltage coil to operate the relay to effect closing of said switch when current flows from said transformer secondary to said network, an impedance connected iii-series with said switch between said network and said transformer secondary whereby said current responsive winding is energized from-said impedance and cooperates with said voltage responsive winding to operate the relay to effect opening of said switch when current flows from said network through said impedance and switch to said transformer secondary.

8. A transformer circuit controlling system for alternating-current networks wherein a switch is provided for connecting and disconnecting the secondary of the transformer and the network, comprising in combination a reactance in series with said switch, a directional relay provided with a V voltage responsive winding and only one current responsive winding adapted to be energized in accordance with the direction of current flow in said reactance when said switch is closed and to be directly energized in accordance with the difi'erence in the magnitudeand phase of the voltage between said transformer secondary and the network when said switch is open, a resistance connected in series with said current responsive winding,

and auxiliary switching means arranged to short circuit said resistance when said switch is closed'and to insert said resistance when said switch is open.

In witness whereof, I have hereunto set my hand this 28th day of'November, 1925. HARRYR. WOODROW- 

